This invention is generally relative to multiband ultra wideband (UWB) communications for short-distance wireless broadband communications.
U.S. Federal Communications Commission (FCC) released the revision of Part 15 of the Commission's rules regarding UWB transmission systems to permit the marketing and operation of certain types of new products incorporating an UWB technology on Apr. 22, 2002. With an appropriate technology, UWB devices are able to operate using spectrum occupied by existing radio service without causing interference. This allows scarce spectrum resources to be used more efficiently. The UWB technology offers significant benefits not only for Government and public safety but also for businesses and consumers under an unlicensed basis of operation spectrum.
In general, FCC is adapting unwanted emission limits for the UWB devices that are significantly more stringent than those imposed on other Part 15 devices. This is to say that FCC limits an outdoor use of UWB devices to handheld devices for the short-distance wireless broadband communications. For an indoor operation of UWB communications FCC provides a wide variety of the UWB devices, such as high-speed home and business networking devices under the Part 15 of the Commission's rules subject to certain frequency and power limitations. In short, the UWB devices must operate in the frequency band from 3.1 GHz to 10.6 GHz. In addition, the UWB devices should satisfy the Part 15.209 limit for the frequency band below 960 MHz and must meet the FCC's emission masks for the frequency band above 960 MHz.
For the indoor operation of UWB communications, Table 1 lists the FCC restrictions of the emission masks (dBm) along with the frequencies (GHz).
TABLE 1Frequency (MHz)EIRP (dBm) 0-960−41.3 960-1610−75.31610-1990−53.31990-3100−51.3 3100-10600−41.3Above 10600−51.3
Outdoor handheld UWB devices are intended to operate in a peer-to-peer mode without restrictions on a location. The outdoor handheld UWB devices have extremely conservative out of band emission masks to address interference with other communication devices. Table 2 shows UWB emission masks for outdoor operations:
TABLE 2Frequency (MHz)EIRP (dBm) 0-960−41.3 960-1610−75.31610-1900−63.31900-3100−61.3 3100-10600−41.3Above 10600−61.3
FCC defines an UWB device where the fractional frequency bandwidth is greater than 0.25 based on the formula as follows:
                              FB          =                      2            ⁢                          (                                                                    f                    H                                    -                                      f                    L                                                                                        f                    H                                    +                                      f                    L                                                              )                                      ,                            (        1        )            where fH is the upper frequency of the −10 dB emission point and fL is the lower frequency of the −10 dB emission point. The center frequency of UWB transmission is defined as the average of the upper and lower −10 dB points as follows:
                              F          C                =                                                            f                H                            +                              f                L                                      2                    .                                    (        2        )            In addition, a minimum frequency bandwidth of 500 MHz must be used for indoor and outdoor UWB communication devices regardless of the center frequency.
Thus, the UWB communication devices must be designed to ensure that the indoor operations can only occur in an indoor environment according to the indoor emission masks as shown in Table 1. The outdoor operations must be according to the outdoor emission masks in Table 2. The UWB communication devices are used for short-range high-speed data transmissions suitable for wireless broadband access to networks.
The UWB communication devices, which are to be developed, are digital radio communications that belong to a wireless broadband communication technology fundamentally. The UWB communication devices transmit a sequence of very short electrical pulses, billionths of a second long, which exist not only on any particular frequency but also on all frequencies simultaneously. The UWB communication devices employ modulated pulses with less one nanosecond in duration. The modulated pulses can be assigned by a digital representation of “0” or “1” according to the transmitted and received pulse based on where the pulses are place in time. In other words, turning the modulated pulses for the wireless broadband communications lies in the timing of the pulses. Therefore, in order to recognize the information in a digital pulse sequence, an UWB receiver has to know the exact pulse sequence used by a transmitter.
Each of the modulated pulses can exist simultaneously across an extensive frequency band if the distributed energy of the modulated pulses at any given frequency exists in the noise floor. Because of the above reason, the UWB devices can co-exist with other communication devices with no discernable interference. Therefore, this opens vast new communications providing tremendous wireless bandwidth to ease the growing bandwidth crunch.
Transmitting the modulated pulses with a very-high data rate over the frequency ranges from 3.1 GHz to 10.6 GHz requires an analog-to-digital (A/D) converter with a very-high sampling rate FS in order to implement the UWB receiver in a digital domain directly. Furthermore, due to the FCC emission limitations of the indoor and outdoor operations, transmitting the modulated pulses should be shaped in such a way that the transmitted pulses must not validate the FCC emission limitation. This leads to high requirements for designing a digital-to-analog (D/A) converter and a transmitter filter in an UWB transmitter. However, it is difficult to design the A/D and D/A converters with such a very high sampling rate for an UWB communication transceiver. In addition, the UWB communication transceiver does not have a flexibility and scalability to transmit and receive the modulated pulses if the UWB communication transceiver is designed to use the entire frequency band from 3.1 GHz to 10.6 GHz as one single-band operation.
The present invention uses a multiband with a multicarrier solution to form 11 multichannels for the UWB communication transceiver. Each multichannel has a frequency bandwidth of 650 MHz, which allows transmitting a data rate at 650 Msps. Shaped pulses that meet the FCC requirements of emission limitations for the indoor or outdoor operation can be transmitted on all of the multichannels at the same time. This is to say that the UWB communication transceiver is able to transmit a total of data rate up to 7.15 Gsps. As a result, the UWB communication transceiver can transmit a data rate with flexibility and scalability. Moreover, the sampling rate of the A/D and D/A converters can be reduced because of using a multiband approach to substitute a single wideband approach. In addition, the present invention is a single device of the UWB communication transceiver, which can be used to deal with a dual-mode indoor and outdoor operation. This leads to saving cost for the UWB communication transceiver.
Thus, there is a continuing need for the UWB communication transceiver employing a new dual-mode shaped pulse architecture based on a multiband and multicarrier solution for the indoor and outdoor operations.